Question

C# groupBox上画图问题

我是个新手，刚学C#， 想做个小程序，结果卡在画图这里了、、详细情况是这样的，有一个按钮G2 ，点一下以后groupBoxG2隐藏，groupBox3出现，并且上面有个坐标。但是写出来代码以后运行，groupBoxG3上没有，只有背景图片，请问怎么回事，哪里出错了？代码如下：
private void buttonG2_Click(object sender, EventArgs e)
{
this.groupBoxG2.Visible = false;
this.groupBoxG3.Visible = true;
Pen blackPen = new Pen(Color.Black, 6);
Point point0 = new Point(300, 300);
Point point1 = new Point(300, 50);
Point point2 = new Point(550, 300);
Graphics g = this.groupBoxG3.CreateGraphics();
g.DrawLine(blackPen, point0, point1);
g.DrawLine(blackPen, point0, point2);
}

Answer 1

为groupBoxG3添加Paint事件处理，将作图代码移入groupBoxG3_Paint中： 

 private void groupBoxG3_Paint(object sender, PaintEventArgs e)
        {
            if(groupBoxG3.Visiable == false) return;
            Pen blackPen = new Pen(Color.Black, 6);
            Point point0 = new Point(300, 300);
            Point point1 = new Point(300, 50);
            Point point2 = new Point(550, 300);
            Graphics g = this.groupBox1.CreateGraphics();
            g.DrawLine(blackPen, point0, point1);
            g.DrawLine(blackPen, point0, point2);
            //释放使用过的作图资源
            g.Dispose();
            blackPen.Dispose();
        }